The invention relates to the components of threaded tubular connections, used for example in petroleum applications, and more precisely the protection of the male end of certain of these components.
Here, by “component” is meant any element or accessory used for drilling or operating a well and intended to be assembled by threading to another component so as to constitute, with this other component, a threaded tubular connection. The component can be for example a tube of relatively great length (in particular of about ten meters in length), a tubular coupling of some tens of centimeters in length, an accessory of these tubes (suspending device or “hanger”, part for change of cross-section or “cross-over”, safety valve, drillpipe connector or “tool joint”, “sub”, and the like).
The components are generally assembled together to be lowered into the oil wells or similar wells and constitute a drill string, a string of casing pipes or liners, or a string of production pipes (“tubing”) (production strings).
Specification API 5CT issued by the American Petroleum Institute (API), equivalent to standard ISO 11960: 2004 issued by the International Organization for Standardization (ISO), covers the pipes used as casing or tubing, and specification API 5B defines standard threads for these pipes.
Specification 7 of the API defines threaded connectors with shoulder for rotating drillpipes.
The manufacturers of components of threaded tubular connections have also developed so-called “premium” threaded connections, which have specific thread geometries, and specific means giving them better performance in service, in particular with respect to mechanical strength and hermeticity.
The aforementioned components have a threaded male end that is intended to be made up into a threaded female end of another drilling or production component. It is therefore essential that their male end suffers the least possible damage, contamination and deterioration between the moment when they leave their manufacturing line and when they are used, as well as between two successive uses. It will be understood that it is in fact necessary to protect, against corrosion, dust and shocks (or impacts), not only the threading, but also any shoulder(s) and stop(s), each of which have specific, complementary functions, in particular for ensuring hermeticity when in use.
The ends of the aforementioned components have generally been coated just before assembly with a grease with anti-galling properties.
It has been proposed, in particular in U.S. Pat. No. 6,933,264, U.S. Pat. No. 6,869,111 and WO 2003/102457, to replace the grease, finally applied by brush on the end of the component, with a thin layer, of predetermined thickness applied in the factory, of a “semi-dry” lubricant free from heavy metals.
It has also been proposed, in particular in U.S. Pat. No. 6,027,145, EP 1211451 and FR 2892174, to replace the grease finally applied by brush on the end of the component, with a thin layer, of predetermined thickness applied in the factory, of a dry lubricant based on particles of solid lubricants.
In these cases with application of a dry or semi-dry lubricant in the factory, it is therefore also and more particularly necessary to provide the best possible protection of the layer of lubricant, with which the ends of the components are coated, both against mechanical removal and against contamination (sand, debris), which are detrimental to the effectiveness of the lubricant.
To provide one or more of these types of protection, generally, as is stipulated in specification API 5CT (in paragraph 12.2), a protective device is fitted on the male and female ends of the components of threaded tubular connections. A great many devices of this type have been proposed, in particular in EP 0148807, US 2006/0042709, WO 2005/075877 and WO 2005/024282, the three last documents relating more particularly to protectors for joints precoated with lubricant in the factory. It has been demonstrated that some of them present risks of damaging the protective device during fitting.
WO2012/028692 envisages an elastomer film between the protector and the component, fixed to the protector by bonding or with a fixing collar, the collar being welded to the protector. The film is provided with a slip agent between the film and the component. The film is in interference with the zone of the imperfect threads of the component. The film is torn during withdrawal of the protector and therefore can only be used once. Hermeticity is low. The assembly is difficult to install on the component. There is a high risk of damaging the film.
Based on their respective embodiments, these known protective devices provide hermeticity downstream of the threading (therefore in a zone the diameter of which is often that of the body or running part of the component) which varies in relation to the dimensional variations of the components. Thus, the outside diameter of a tube body according to specification API 5CT can vary by + or −0.79 mm for tube bodies with diameter less than 114.3 mm and from −0.5% to +1% of the diameter for tubes with diameter greater than or equal to 114.3 mm (i.e. from −0.89 mm to +1.78 mm for a tube body with a diameter of 177.8 mm).